Unexpected Lessons Learned from Mid-Century Atomic Bomb Explosions
In , a Swedish stem cell biologist at the Karolinska Institute in Stockholm, Jonas Frisen, decided to see if he could date people using the same technique. Frisen had studied pine trees and knew about the carbon atomic bomb spike. He also reasoned that people eat the products of trees -- apples, pears, peaches, olives, almonds, walnuts -- and we also eat the animals that eat the fruits of trees, so he decided to see whether atomic testing had affected human cells.
At a cellular level, he surmised, we are affected by what we eat, so he performed autopsies on two sets of humans. One group was born in the mids during the era of atomic testing. The second group was born later, in the '60s, after the test ban treaty.
When Frisen examined some brain cells in both groups, he discovered that humans born in the '50s have more carbon in their DNA, so the spike we see in trees is echoed in humans. This allowed him to age or "date" a person by examining the brain cells -- a high carbon count means the person was conceived in the era of atomic testing. That's not a test you'd want to try at home, because rather than extract a brain cell, you can always ask your parents when you were born -- but it did lead Frisen down some interesting paths.
The amazing lesson of all this is that a bunch of atomic bomb blasts from 50 years ago changed the biology of the world, searing themselves into most living things, and the evidence is still there.
How A-Bomb Testing Changed Our Trees : Krulwich Wonders : NPR
If you were born around or shortly thereafter, those bombs made their mark -- in you! We incorrectly described the process by which nuclear testing produced a spike of carbon atoms in the atmosphere. We should have said, "Each atomic blast released a lot of neutrons into the atmosphere, many of which slammed into nitrogen atoms floating by, which turned those nitrogen atoms into carbon atoms.
The immediate environmental effects of nuclear bomb testing during the Cold War era were undoubtedly devastating. Having left enormous negative environmental and socioeconomic impacts all over the world, it is hard to imagine that any sort of silver lining to these tests could exist.
But despite all the destruction that these tests caused, their remnants are now being used to answer questions in biology that might otherwise have been unsolvable or, at the least, extremely difficult to study. Indeed, nuclear bombs set off in the s and s left a distinct environmental signature that is now being used to determine why certain body parts heal better than others, how often various tissues are replaced as you age, and providing us greater insight into the basis of many aging-related diseases.
Atomic bomb testing resulted in a huge influx of carbon into the atmosphere.
Carbon is a key component of many of the most intricate structures in our universe, from diamonds to DNA. Carbon is an extremely rare form of carbon, referred to as a radioactive isotope that has 8 neutrons instead of the usual 6 Figure 1. Unfortunately, while these tests were performed in remote areas, their effects were not confined to their respective detonation sites.
The influx of carbon into the atmosphere also led to increased carbon levels in all living things, including plants, animals, insects, and humans. Since nuclear bomb testing was banned in the early s, carbon levels have steadily been on the decline.
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Carbon is absorbed by humans through a variety of sources including inhalation, drinking water, and diet. Radioactive isotopes, like carbon, are unstable and decay over time. Every time a cell divides, it first replicates its genetic material, DNA, and this DNA incorporates a significant amount of carbon, which can include carbon Figure 3. Since carbon takes so long to decay, it can be assumed that the amount of it in a molecule of DNA will remain the same as long as the cell does not divide.
Thus the amount of carbon present in human tissue is reflected by the levels in the environment at the time that that tissue was formed.
Nuclear Bombs Made It Possible to Carbon Date Human Tissue
Tissues with a high turnover rate will have carbon levels similar to current atmospheric levels, and tissues with a low turnover rate will reflect previous atmospheric levels. Analysis of the carbon to carbon ratio can reveal when a cell division occurred with a very high degree of accuracy, because unlike other components of cells, DNA remains static. This enables scientists to use carbon concentrations to estimate the age of tissues for people who lived during and after the carbon bomb pulse.
Joints and tendons are frequently injured and associated with chronic pain and poor healing. Carbon dating studies have revelead that the Achilles tendon is not renewed after the first 17 years of life and has poor regenerative capacity.
Similarly, a recent study on the articular cartilage of the human knee found that there is essentially no turnover of this joint cartilage once an individual reaches adulthood. Herbivores lag the atmosphere slightly because their primary carbon source is on the order of months old. Omnivores and carnivores lag the atmosphere further because their carbon sources are another step removed.
However, it has been confirmed that atmospheric 14 C levels from the bomb pulse closely correlate with 14 C found within dietary components from that given year and that the annual 14 C averages in food match those found in human tissue. Within organisms, tissues turn over at different rates so 14 C levels vary between tissues.
What is the Bomb Effect?
The date of formation of a tissue or specific biomolecule can be estimated from the bomb-curve by considering these lags in incorporation and relating the 14 C concentration with the date. Using an annual average of the carbon intake over a growing season can account for much food chain lag and produce a usable curve Figure 1. Caution must be exercised when dating an elevated sample since the pulse is double valued. Placing a sample on the ascending or descending side of the pulse can often be accomplished if other information is available.
The precision of bomb-pulse dating depends on the ability to measure the 14 C concentration in a sample and the slope of the curve.